Intense emotions such as anger and fear are known triggers of sudden cardiac death (SCD), particularly in the context of coronary artery disease (CAD). However, the role of typical daily emotions in SCD is an understudied phenomenon. We have recently demonstrated in patients with Long QT Syndrome at genetic risk for SCD that everyday emotional states are reliably related to repolarization duration, an index of electrical instability of the heart and SCD risk. This finding indicates that typical daily emotions may be one of many factors that affect SCD risk. A critical next step is to determine whether everyday emotions influence repolarization, ischemia (shortage of blood delivered to heart muscle) and/or their interaction in patients with CAD, and whether these effects vary as a function of CAD severity. It is also important to determine whether these associations are observed in healthy comparison subjects and whether the association between typical daily emotion and repolarization varies as a function of age. Four groups of 100 subjects each will be studied: two groups of patients with established CAD (low risk: documented CAD but no history of life-threatening arrhythmias; high risk: prior myocardial infarction plus cardioverter-defibrillator implanted for primary prevention) and two groups of comparison subjects with verified absence of CAD (older: age- and sex-matched to CAD subjects, negative exercise stress ECG / echocardiogram and negative cardiac disease history; younger: age range 21-50 years, normal ECG and negative symptom history). Subjects will be studied for three consecutive days during their routine daily activities in their typical home and work environments. Momentary ratings of emotional state will be randomly elicited 7-10 times per day and ambulatory (Holter) ECG monitor recordings will be continuously obtained. During 5-minute epochs corresponding to each set of momentary emotion ratings, Holter recordings will be assessed for repolarization duration (QT interval corrected for heart rate) and ischemia (ST segment changes). The proposed project by an experienced team of investigators and consultants involves the application of a proven set of methods to a new clinical setting (CAD). If it were shown that typical daily emotions reliably alter repolarization and ischemia in the context of CAD, it would expand our understanding of the role of emotion in SCD risk and would provide a strong impetus for preventive interventions designed to minimize the harmful effects and enhance the beneficial effects of daily emotion on the heart.